The goal of this Mentored Patient-Oriented Research Career Development Award (K23) is to develop the candidate, Dr. Zachary Adams, into an independent investigator prepared to lead large-scale, rigorously designed studies evaluating the utility of mobile health (mHealth) technologies in improving treatment efficiency, efficacy, and reach among high-risk youth with substance use disorders (SUD) and comorbid mental illness. Comorbidity is common in adolescence and often complicates treatment progress. Use of mHealth approaches-such as mobile applications that tailor content to patients' specific needs, enhance patient engagement, and facilitate existing evidence-based treatments-holds great promise in reducing the public health burden of addiction and mental illness. This application proposes training and Stage IA-IB intervention development research that is directly in line with NIDA-supported initiatives and represents a logical progression from the candidate's prior research and training to address career development goals in six areas: (1) development of mobile applications for adolescent mental health, (2) etiology and treatment of comorbid SUD and trauma-related mental illness in adolescents, (3) conduct and evaluation of clinical trials, (4 multilevel and longitudinal data analysis, (5) grant management, and (6) research ethics. Goals will be accomplished through high caliber didactic training, participation in national conferences and institutes, and hands-on research experience. Activities will be completed under the mentorship of an accomplished team of expert on-site investigators in the fields of adolescent comorbidity and integrated treatments (Danielson), mHealth methodologies and evaluation (Treiber), technology-based mental health interventions (Ruggiero), [qualitative and mixed methods research (Pope)], and analysis of longitudinal, clinical trials data (Ramakrishnan). The candidate will apply these skills through completion of a three-component research project: (I) initial design and programming of a novel web-based mobile application to enhance outpatient treatment for comorbid SUD and posttraumatic stress disorder, (II) mixed method usability testing of the application by adolescents and providers to guide design and content refinements, and (III) a pilot trial to demonstrate the feasibility of the proposed methodology and to evaluate the preliminary efficacy of the application to guide design of an randomized controlled efficacy trial. An iterative, patient- and provider- centered development process will be employed to ensure relevance to the target population. The central hypothesis is that developmentally tailored mobile applications that incorporate evidence-based treatment principles can facilitate increased patient engagement in and between sessions, thus improving the efficiency, efficacy, and reach of treatments for this highly vulnerable population. After completing these projects, there will be a better understanding of how mHealth approaches can be used to augment existing treatments for comorbid SUD and mental illness. The experience, and data gained from this project will position the candidate to pursue future NIH funding to build this line of researc and to adapt and test future mHealth tools for adolescent substance abuse and mental health problems.